Monk is pretty easily the top single target dps, but it needs to be constantly hitting otherwise it will lose greased lightning and a decent chunk of dps. Dragoon is second highest and it is easier to maintain it's dps. Then comes ranged classes. It is made that way deliberately to offset how much more time melee spend out of combat range compared to ranged classes. Bard is probably the lowest maximum dps simply because it never has to stop damaging. I haven't personally tested it, so this is just an assumption.

Doesn't matter though, because all of the classes even out in terms of actual combat dps. I don't think more cross class skills would really affect these ranking by much.